Audiometric tests are used for performing hearing screening, comprehensive diagnostic assessment, and audiological research. Audiometric testing systems provide a means to elicit and acquire signals evoked in response to appropriate auditory stimuli. Some common audiometric testing systems are: behavioral audiometry; auditory evoked potentials (AEPs) that include auditory brainstem responses (ABRs); and auditory steady state responses (ASSRs), and otoacoustic emissions (OAEs).
Three common types of sound-delivery devices for audiometric testing are headphones, insert earphones, and ear probes. Each of these sound-delivery devices has a coupling interface with the patient's ear during testing. This coupling interface is responsible for delivering a sound stimulus to the ear, as well as providing a seal to the ear to reduce ambient background noise that might interact with the delivered stimulus and influence measurements. These coupling interfaces may be an integral part of the sound-delivery device (as in the case of headphones) or offered as optional accessories (as in the case of eartips for insert earphones and ear probes).
Audiometric headphones include both over-the-external-ear (“circumaural”) and on-the-external-ear (“supra-aural”) varieties. These devices contain both the sound-transducer device circuitry as well as the coupling interface/cushion used to deliver the sound stimulus to the patient. In the case of circumaural headphones, the coupling interface is provided by ear “cups” that fully enclose the entire external ear (similar to full-sized headphones used to listen to music). This interface creates a fully-closed seal that provides acoustic isolation to effectively block out any ambient background noise and minimize leakage of sound to the outside environment, as well as providing enhanced sound quality and improved low-frequency response performance. In the case of supra-aural headphones, the coupling interface is provided by ear “pads” that are applied on the ear (similar to the relatively compact, ear pad headphones used to listen to music). Since these pads rest on the outer ear, the coupling interface is not fully sealed, and therefore this interface may offer poor background noise exclusion and inferior interaural (i.e., between the ears) attenuation. Typical materials used to manufacture the ear cups and pads of the headphones include polyurethane foam, silicone, various rubbers, and elastomers. Both circumaural and supra-aural headphones are comfortable to wear, easy to apply, and require no special training to use since no object is inserted into the patient's ear canal. However, these headphones can cause interference with earrings, glasses, and hairstyles, and cause unwanted electromagnetic interference near the ear. Also, since they typically do not contain any disposable components, the earphone cushions and headbands may need cleaning to be sanitary.
Audiometric insert earphones and ear probes are intra-aural (in the ear) devices that perform the same intended function as audiometric headphones, except a small end piece is inserted into the ear canal. This insertion can provide an effective seal that provides isolation from external noise. Both insert earphones and ear probes are compact and lightweight, and due to their small sizes, there is little to no interference with earrings, glasses, hairstyles, etc. Audiometric insert earphones typically includes an isolated transducer case (that houses the sound transducer device circuitry) and a hollow tubing that connects to an adaptor/eartip to convey the stimulus signal from the sound transducer to the patient's ear. Ear probes, on the other hand, combine both the transducer circuitry and transmission tubing into one casing. Both audiometric insert earphones and ear probes are coupled to the patient's ear by means of disposable or reusable accessories to deliver the sound stimulus. These accessories have been classified by some manufacturers as “earphone cushions” that come in two varieties: eartips and/or ear cups.
Eartips are small “plugs” that connect to the sound output ends of audiometric earphones and ear probes and are inserted into the patient's ear canal to provide a coupling interface between the earphone or ear probe and the ear. Since the patient's ear canal is fully sealed, eartips can provide effective background noise reduction and increased interaural attenuation. These plugs are typically made of polyurethane foam, silicone, or various elastomers, and come in a variety of shapes and sizes suitable for both adult and infant testing. They are typically single-use, disposable devices, and do not require high overall maintenance. An appropriate insertion depth (fit) is used for a proper seal and ambient sound attenuation.
An ear cup is an alternative sound-delivery device accessory used with some audiometric testing systems. Ear cups offer a compromise between the coupling interfaces for audiometric headphones and earphones or ear probes, by providing an additional intermediary interface between the earphone or ear probe and the ear. Like eartips, ear cups attach to the sound output end of an earphone or ear probe (using the stimulator's own tip, a separate eartip, or an adaptor). Like headphone cushions, ear cups are placed over the entire external ear during audiometric testing, without inserting an eartip into the patient's ear canal. Since the ear cup covers the entire ear, it can provide an effective seal against background noise and offer good interaural attenuation. Ear cups are typically disposable, thus requiring no maintenance, are comfortable to wear, are easy to apply, and do not require much training to use since there is no insertion into the patient's ear canal. Typical materials used to manufacture ear cups include polyurethane foam, silicone, and various elastomers. The portion of the device that makes skin contact with the patient is a thin layer of adhesive, such as a skin contact adhesive or hydrogel, used to adhere the device onto the skin of the patient's head.